FIGS. 1 through 3 show a stapleset brush 900 in accordance with the prior art.
As can be seen in the perspective view of the stapleset brush 900 in FIG. 1, brush bristles 905, represented in FIGS. 1 through 3 as a bundle of individual bristles, extend from drilled or molded holes 901 in a solid block of material such as rubber, leather, metal, or wood serving as base 902. As can be seen from the side sectional view of FIG. 2, the side shown at FIG. 2 being the same side as faces the reader in FIG. 1, brush bristles 905 contain tufts or bundles of strands that are folded over, the folded portion being held against the surface at the bottom of the hole 901 by a wire staple 907 or other rigid fastener. This is shown in the end sectional view of FIG. 3, the end shown at FIG. 3 being, for example, the end at the right in FIG. 1. At FIG. 3, it is possible to see the profile of the staple 907, this being such that the ends of the staple 907 are embedded and held firmly within the bulk material of the base 902.
Several difficulties arise when one attempts to employ the stapleset structure 900 of the prior art shown in FIGS. 1 through 3 as a belt brush or in another such application where flexibility is required.
For example, a belt brush employed in a conveyor or cleaning application might be made to undergo flexible deformation as it is driven within the transport mechanism of which it forms a part. For example, a belt-driven conveyor brush or cleaning brush in such an application might be driven by pulleys or made to wrap around idlers that cause the brush to bend around the radius of curvature of the pulley or idler. However, where the base 902 is fashioned from a rigid material such as metal or wood, the stapleset brush 900 will, needless to say, be inflexible and thus unsuitable for use as a belt brush in such an application.
Furthermore, even where the base 902 is fashioned from a less rigid material such as rubber, the fact that the staple 907 is typically stiffer than the material of the base 902, which is to say that the staple 907 and the base 902 in such case would have dissimilar moduli of elasticity, can cause localized stresses to occur in the vicinity of the staple 907, such stresses being made all the more severe to the extent that the staple 907, which is typically fashioned from a cut piece of wire, has sharp ends, corners, or edges. Such stresses can cause increased wear, shortened life, and failure of the stapleset brush 900. Of course, any stresses arising due to presence of the staple 907 will only be aggravated and made more intense by flexible deformation of the sort that such a belt brush will typically be made to undergo, further contributing to increased wear, shortened life, and failure of the stapleset brush 900.
Moreover, to properly embed the staple 907 within the base 902, the base 902 must have a certain minimum height, the height direction here being the direction in which the bristles 905 extend from the base 902 in FIGS. 1 through 3. However, thickness of the base 902 in this height direction contributes to the second moment of inertia about an axis perpendicular to a plane formed by the face of the base 902 indicated in, for example, FIG. 2. Specifically, the thickness of the base 902 in the height direction causes the base 902 to resist bending such as would cause the ends of the base 902 to flex so as to conform to a radius of curvature centered on an axis emerging from the plane of the base 902 at a point above or below the stapleset brush 900 as viewed in FIGS. 1 and 2. Forcing the base 902 of the stapleset brush 900 to conform to such a radius of curvature despite this stiffness or resistance to bending due to the large second moment of inertia, as might be done were the stapleset brush 900 to be employed as a belt brush driven by pulleys in a transport mechanism, for example, would create high stresses in the base 902, both in the vicinity of the staple 907 as well as in the vicinities of the top and bottom of the base 902. Such stresses can also cause increased wear, shortened life, and failure of the stapleset brush 900.
In addition, in a structure in which the bristles 905 contain tufts that are folded over and attached by stapling to the base 902, there will of necessity be gaps between adjacent tufts due to presence of the wall containing base material 902 serving as partition between adjacent holes 901. In the structure shown in FIGS. 1 through 3, bristle density will be discontinuous along the length direction (i.e., the direction extending from left to right in FIG. 1 or FIG. 2), bristle density being high where bunched bristles 905 emerge from a hole 901, and being low between holes 901 where no bristles 905 emerge. This effect can to some extent be mitigated by employing a design in which bristles 905 fan out from their proximal regions, where they emerge from the holes 901, to their distal regions, where the bristles 905 collectively form a bristle end zone. Depending on the application in question, this bristle end zone might serve as conveyor drive face for transport of small objects including, but not limited to, nuts, bolts, pills, and/or other such objects to be conveyed, might serve as cleaning brush for cleaning parts or surfaces, or might serve as sealing surface for sealing a shuttle canister within a pneumatic tube transport system for use at a bank drive-up window, for example. Nonuniformity in bristle density within the bristle end zone can cause poor conveyor drive characteristics in an application in which the bristle end zone serves as conveyor drive face, poor cleaning performance in an application in which the bristle end zone serves to sweep or scour a floor or other surface, poor sealing in an application in which the bristle end zone serves as sealing surface, and other performance problems. In addition, the gaps that exist between adjacent tufts impose a limit on the maximum bristle density that can be achieved, and this limit on maximum achievable bristle density can also adversely impact achievable bristle end zone characteristics.
In such a design according to the prior art, there are practical limits to the width (i.e., the direction extending from left to right in FIG. 3) of the bristle end zone formed by the bristles 905 that can be achieved. For example, beyond a certain width, it may be difficult for the staple 907 to retain the bristles 905 at all points along the bottom of the hole 901. Furthermore, as can be seen in FIG. 3, proper embedding of the staple 907 within the base 902, such as will prevent the cut ends of the staple 907 from protruding from the sides of the base 902, necessitates that there be a certain minimum wall thickness to either side of the hole 901 in the width direction (i.e., the direction extending from left to right in FIG. 3). This being the case, even if one were to, for example, laminate multiple flexible strip brush elements together in side-by-side fashion in an attempt to extend the effective width of the brush, a stapleset brush 900 having design as shown in FIG. 3 would be limited with respect to the density of bristles 905 that is achievable in the width dimension due to presence of this minimum wall thickness to either side of the hole 901 in the width direction, in similar fashion as the limitation presented by the thickness of the wall serving as partition between adjacent holes 901 in the length direction which was described above.
The physical properties of the material employed as bristles 905 will in general impose constraints on overall tuft height, width, and length. For example, if the bristles 905 contain polypropylene or other such thermoplastic substance or other material having similar modulus of elasticity, mechanical properties of the material employed for the bristles 905 will limit the dimensions of the bristles 905 to certain practical ranges from the standpoints of manufacturing and performance.
For example, to achieve a brush 900 having bristles 905 with the requisite physical characteristics for the application in question, and in particular to achieve a brush 900 having such desired physical characteristics at the ends of the bristles 905 forming the bristle end zone, it will in general be necessary to impose limits on the ranges that can be employed for bristle length and diameter, and such ranges will be further limited upon considering the requisite average bristle density (e.g., number of bristles per square inch) and allowable nonuniformity in that bristle density.
For these and other reasons, a stapleset brush 900 manufactured in accordance with the prior art as shown in FIGS. 1 through 3 will often be inadequate except when employed in a comparatively narrow assortment of limited configurations. For example, as explained above, the stapleset brush 900 of the prior art may be inadequate where width is desired at the bristle end zone formed by the ends of the bristles 905, where high bristle density is desired at the bristle end zone formed by the ends of the bristles 905, where good uniformity in bristle density is desired at the bristle end zone formed by the ends of the bristles 905, or where it is desired that the stapleset brush 900 exhibit good flexibility with respect to flexure about an axis perpendicular to the plane of the bristles 905, such as would be the case were the stapleset brush 900 to be fashioned in an endless loop for driving by pulleys and idlers.
Although the difficulties mentioned above by way of example are described as applying to the stapleset structure 900 of the prior art shown in FIGS. 1 through 3, one or more of the foregoing difficulties may apply to structures from the prior art other than those shown in FIGS. 1 through 3. Furthermore, while various aspects and embodiments of the present invention may overcome one or more of the difficulties described above, not every difficulty mentioned above is necessarily overcome by all aspects and embodiments of the present invention, and in fact there may be aspects and embodiments of the present invention that overcome difficulties in the prior art other than those mentioned by way of example above.
Whether such difficulties exist in the prior art shown in FIGS. 1 through 3 or in other structures from the prior art that are not shown, a heretofore unaddressed need exists in the industry to address such deficiencies and inadequacies.